AT Athleta’s packed fitness studio in the Flatiron District, Danielle Wechsler hands out pompoms before bounding to the front of the room with a pair of her own.
“Remember to smile,” the 28-year-old chirps, beaming, as she leads the group in jumping jacks and squats, part of her warmup set to hip-hop music.

No, this isn’t some home for aging cheerleaders trying to recapture their glory days. It’s CheerFIT, a fitness class inspired by rah-rah routines.

Contrary to stereotypes, cheerleading “isn’t just standing on the sidelines with short skirts and pompoms,” says Wechsler, who cheered at Syracuse University from 2005 to 2009. There’s sweating, grunting and the sound of pompoms shaking after the class lands a simple dance routine that involves pivoting, hip motions and, yes, smiling.

“The class is built on the foundation of balance, coordination and control,” says Wechsler, who designed it to build the muscles — arms, legs and core — that cheerleaders need to tumble, build endurance and prevent injuries. There are stretches, lunges, cheer-inspired exercises and cardio intervals culminating in an abs workout and a one-minute plank.

Wechsler started offering her hourlong CheerFIT classes in April 2014 and has since hired more than 15 instructors to keep up with the demand. Ranging from $10 to $30, the classes meet at several gyms, including Retro Fitness, Power Studios and the aforementioned Athleta, where Wechsler leads free classes on Thursdays. Starting May 9, she’ll teach a five-day, $50 cheer boot camp in Central Park.

So far, the workout is giving New Yorkers another reason to smile: They’re losing weight while gaining strength.

Taylor McPherson, 25, says she dropped 23 pounds since starting the class in January. “I actually have my own pompoms that I bring to class with me,” says the Asbury Park, NJ, resident, who’s in marketing and takes CheerFIT sessions twice a week.

Wechsler began hashing out her program nearly seven years ago after tearing the ACL in her knee during her junior year. Rather than having it surgically repaired, she opted for physical therapy, and was back cheering on the school’s football and hoops teams by her senior year.

“After three months, I outgrew the physical-therapy program and used what I knew from cheerleading to strengthen my knee from there,” says Wechsler, who also consults within the fitness industry on business development.

And yes, she says, men have taken her classes, though they choose to use weights: “After class, they always come up and say it was super hard — like [the] Insanity [workout] with pompoms.”